The present invention relates to a voice transmitting apparatus, which is provided between a switching device and a transmission path and performs cell assembly and cell disassembly of a voice band signal so as to transmit/receive the signal, a voice transmitting method, and a voice band signal transmitting system using the same apparatus or the same method.
Conventionally, when a voice band signal is transmitted/received, a single channel was assigned to the voice band signal on a single line with the use of time division multiplexing. In the time division multiplexing, since the channel is occupied even in a state of no calling, there occurred a waste of a transmission path. In order to utilize the transmission path effectively, highly effective compression-encoding and decoding of a voice are performed. The compression-encoded voice is then divided into frames, thus forming a cell as shown in FIG. 2. Also, in FIG. 2, reference numeral 1 designates the cell, numeral 2 designates a header area, and numeral 3 designates a data area. In transmitting/receiving the cell 1 formed in this way, the following method is being carried out: The cell 1 is forced not to be transmitted/received at the time of no sound in the voice band signal, thereby making the transmission path available for the other lines at the time of no calling and thus allowing the transmission efficiency to be statistically enhanced. However, concerning a voice band data signal in devices such as a facsimile and a modem, unlike the case of the voice band signal, the above-described method is incapable of performing the highly effective voice compression-encoding and of stopping the cell at the time of no sound. Accordingly, on a line for the voice band data signal in devices such as the facsimile and the modem, signaling information was referred to so as to carry out a process of stopping the cell transmission when the line is unused, thus intending to utilize the transmission path effectively.
However, in a voice transmitting apparatus which performs cell assembly and cell disassembly of the voice band signal constituted as described above and in a voice band signal transmitting system which has a switching device employing a common line signal system, when transmitting/receiving the voice band data signal in devices such as the facsimile and the modem, it is impossible to refer to the signaling information and thus the cell transmission is permitted to be continued even when the line is unused. This resulted in a problem that it is impossible to enhance utilization efficiency of the transmission path.
The present invention aims at solving the above-mentioned problem in the prior art. An object thereof is to provide a voice transmitting apparatus which, even when transmitting/receiving the voice band data signal in the voice band signal transmitting system using the switching device based on the common line signal system, makes it possible to stop the cell transmission when the line is unused and thus to enhance the utilization efficiency of the transmission path, a voice transmitting method, and a voice band signal transmitting system using the same apparatus and the same method.
In order to attain this object, a voice transmitting apparatus related with the present invention, which is employed in the voice transmitting apparatus, the voice transmitting method and the voice band signal transmitting system using the same apparatus and the same method, is characterized by comprising a cell assembling means for assembling a voice band signal, which is obtained from a switching device through a switching device interface means, into a cell so as to transmit the cell to a transmission path through a transmission path interface means, an up data judging means for judging, from the voice band signal, a line-unused time of signal which the switching device outputs when a line is unused, a cell disassembling means for disassembling the cell, which is received from the transmission path, back into the voice band signal again, a down data judging means for judging the line-unused time of signal from the voice band signal obtained from the cell disassembling means, a timer for counting a continuation time from the moment when both the up data judging means and the down data judging means judge that the line-unused time of signal coincides with the voice band signal, and a protection time judging means for judging a protection time, during which a continuity of the continuation time counted by the timer is monitored for a fixed time period, so as to control stopping of a cell transmission by means of the cell assembling means after a lapse of the protection time.
Also, the voice transmitting apparatus is characterized in that the above-described up data judging means and down data judging means judge data row, which is set arbitrarily based on characteristics of user data, as the line-unused time of signal.
Also, the voice transmitting apparatus is constituted so that the above-described protection time judging means, taking advantage of the protection time set arbitrarily based on characteristics of the user data, monitors the continuity of the continuation time which is counted by the timer in accordance with the judgement results obtained by the up data judging means and the down data judging means.
According to the above-mentioned constitution, the cell assembling means assembles a voice band signal, which is obtained from the switching device through the switching device interface means, into a cell so as to transmit the cell to the transmission path through the transmission path interface means, further the up data judging means judges, from the voice band signal, a line-unused time of signal which the switching device outputs when the line is unused, also the cell disassembling means disassembles the cell, which is received from the transmission path, back into the voice band signal again and transmits the voice band signal to the switching device, furthermore the down data judging means judges the line-unused time of signal from the voice band signal obtained from the cell disassembling means, the timer counts the continuation time in accordance with judgements made by both the up data judging means and the down data judging means concerning coincidence of the line-unused time of signal with the voice band signal, the protection time judging means judges the protection time, during which the continuity of the continuation time counted by the timer is monitored for a fixed time period, so as to control stopping of the cell transmission by means of the cell assembling means after a lapse of the protection time, and when either the up data judging means or the down data judging means judges a signal other than the line-unused time of signal from the voice band signal, it is possible to clear the continuation time counted by the timer and at the same time to control starting of the cell transmission by means of the cell assembling means with the use of the protection time judging means.
Also, a row of predetermined data bits acting as a signal indicative of a line-unused time, which is judged to coincide with the voice band signal, is set arbitrarily based on characteristics of the user data, thus making it possible to control stopping or starting of the cell transmission even if the voice compression system is altered or regardless of the presence or absence of the compression.
Also, the protection time in connection with the protection time judging means is set arbitrarily based on characteristics of the user data, thereby making it possible to stop the cell transmission when the line is unused and thus to aim at enhancing utilization efficiency of the transmission path.
Moreover, in the voice band signal transmitting system which has the switching device employing the common line signal system, even when transmitting/receiving the voice band data signal in devices such as the facsimile and the modem, the voice transmitting apparatus or the voice transmitting method makes it possible to stop the cell transmission when the line is unused and thus to enhance the utilization efficiency of the transmission path.